The present invention relates to a method for preparing lactam imides which are useful as initiators for anionic polymerization of lactams.
In G.B. No. 1,102,521 there is disclosed a method of producing N-acyl caprolactams and di-acyl bis-caprolactams by reacting a carboxylic acid, preferably a dicarboxylic acid, with acetyl caprolactam. This process, however, is economically disadvantageous as well as being inefficient because the preparation and isolation of N-acetyl caprolactam requires a separate process step. That is, first one must react epsilon-caprolactam with acetic anhydride. The acetic acid which is eliminated as the reaction proceeds is removed by distillation. Only after this step is completed and the N-acetyl caprolactam is formed and isolated can one proceed to prepare the N-acyl caprolactam by reacting the N-acetyl caprolactam with carboxylic acid. There is a need, therefore, for a more efficient and versatile process which can be performed in one step without the need for isolating intermediate products and which can be used to prepare a variety of lactam imides.